Melatonin modulates allergic lung inflammation

Asthma is an inflammatory lung disease characterized by cell migration, bro nchoconstriction and hyperresponsiveness, and can be induced, as an experim ental model, by ovalbumin sensitization followed by a challenge. In additio n to the well-known immunostimulatory effects of melatonin, research has id entified some of its anti-inflammatory properties. In this study, we evalua ted the influence of pinealectomy and melatonin administration on cell migr ation in an experimental model of allergic airway inflammation. We evaluate d, in pinealectomized rats treated or not with melatonin, cell migration in to the bronchoalveolar fluid, the number of cells and their proliferative a ctivity in the bone marrow, and plasma corticosterone levels. Pinealectomy reduces, 24 hr after the challenge, the total cell number count in the lung and bone marrow cell proliferation, without changing the number of cells i n the bone marrow or in the peripheral blood. This fact suggests that melat onin is important in the control of cell recruitment from the bone marrow a nd the migration of those cells to the lung. Melatonin administration to pi nealectomized rats seems to restore the ability of cells to migrate from th e bone marrow to the bronchoalveolar fluid. So, the development of specific inhibitors of melatonin would benefit patients with asthma.